This invention relates to an optical image transformation apparatus and, in particular, to an optical image transformation apparatus which has a plurality of photocells, a memory, and a function generator, and outputs a total sum of output signals of the desired photocells in accordance with data associated with a weighting function generated by the function generator and stored in the memory, so that two-dimensional transformation of an optical image can be executed spatially-parallelly in real time.
Conventionally, the following two types of sensing devices for detecting and measuring an optical image or a spatially distributed pattern of irradiation light intensities and for extracting useful data are known.
(1) a device for transforming an image detected by a light-receiving section into electrical signals, and sequentially outputting the signals like a charge-coupled device (CCD); and
(2) a device for outputting signals, in real time, which have been simultaneously processed in accordance with a spatial weighting function like an integrated spatial filter using a slit array.
As the latter device, those described in Japanese patent application No. 60-155462 "Non-contact Diameter Measuring Apparatus", Japanese patent application No. 60-155463 "Non-contact Diameter Measuring Apparatus", Japanese patent application No. 60-155464 "Non-contact Type Diameter Measuring Apparatus", and Japanese patent application No. 60-155465 "Non-contact Type Diameter Measuring Apparatus" by the same inventors as those of this invention are known. In these apparatuses, a slit array type spatial filter such as a photodetector array consisting of 2n rectangular photodetectors having the same dimension is used. These apparatuses execute spatially-parallel signal processings and output signals, in real time, the signals including data associated with a moving speed of a projected circular image and its diameter.
A "Variable Spatial Filter" described in Japanese patent application No. 61-64694 by the same inventors as those of this invention is also known as another example of the latter device. In this filter, a weighting function can be variable, and a signal processing scheme can be modified based on the variable weighting function.
The literature "Bildverarbeitung mit Orthogonaltransformation" Nachrichtentech Electron., Vol. 35(4), pp. 152-154 (1985), which is also another example of the latter device, proposes an idea for realizing an optical filter which uses two-dimensional orthogonal functions of two values "0" and "1" as an optical transmission intensity by a variable liquid-crystal matrix and performing spatial filtering in accordance with these functions as a weighting function. With this idea, the liquid-crystal matrix can serve as an optical filter having a spatial transmittance profile in accordance with the two-dimensional orthogonal function although it has two values of "1" and "0", i.e., a light-transmitting state and a light-shielding state. More specifically, the liquid-crystal matrix is nothing but a spatial filter. Since the liquid-crystal matrix has a variable property, although only two values of "0" and "1" are used, a plurality of types of spatial filters can be selectively realized due to external settings.
In the conventional devices of the former type, like a CCD, a detected image is transformed to time-serial electrical signals and the signals are sequentially output. Such a device can be connected to a versatile external signal processing system, can perform various kinds of signal processing, and can extract useful data. However, in such a device, when the signals are transferred to the processing system, all the image data must be sequentially transferred, and a predetermined time is required for image transfer. Therefore, the device cannot follow an object which moves faster than the predetermined time, and cannot obtain dynamic data for high speed objects.
A conventional device, such as the integrated spatial filter described above, performs parallel signal processing in accordance with a spatial weighting function to output signals including useful data in real time. Such a device is useful in obtaining dynamic data such as moving speed and direction of the high speed object. However, the device is not useful in changing the weighting function. Therefore, in such a device, signal processing is fixed, and cannot be modified.
The above-mentioned variable spatial filter is useful in changing a weighting function depending on the moving direction of an object and measuring moving speeds in various directions, but does not have the capability of performing two-dimensional transformation.
In signal processing utilizing two-dimensional orthogonal functions with the liquid-crystal matrix described in the above-mentioned literature, high voltage is required for driving the liquid crystal. High-speed switching cannot be performed, and the size of the device cannot be reduced.